“Color-plus-clear” coating systems involving the application of a colored or pigmented basecoat to a substrate followed by application of a transparent or clearcoat over the basecoat have become increasingly popular as original finishes for a number of consumer products including, for example, cars and floor coverings such as ceramic tiles and wood flooring. The color-plus-clear coating systems have outstanding appearance properties such as gloss and distinctness of image, due in large part to the clear coat.
“One coat” systems comprising a one coat color layer are applied themselves as the topcoat. One coat systems are frequently used for household appliances, lawn and garden equipment, interior fixtures, and the like.
Many of the coatings used in both the color-plus-clear systems and one-coat systems are powder coatings. In recent years, powder coatings have become increasingly popular because these coatings are inherently low in volatile organic content (VOC). The low VOC significantly reduces air emissions during application and curing as compared to liquid coatings. Liquid coatings are still used in many systems, however, particularly those wherein solvent emissions are permitted. For example, the coating of elastomeric automotive parts is often done by spraying liquid compositions.
Topcoat film-forming compositions, such as the protective and/or decorative one coats for household appliances and the transparent clearcoat in color-plus-clear coating systems for automotive applications, are subject to defects that occur during the assembly process and damage from both the environment and normal use of the end product. Paint defects that occur during assembly include the paint layer being too thick or too thin, “fish eyes” or craters, and under-cured or over-cured paint; these defects can affect the color, brittleness, solvent resistance and mar and scratch performance of the coating. Damaging environmental factors include acidic precipitation, exposure to ultraviolet radiation from sunlight, high relative humidity and high temperatures; these factors can also result in compromised performance. Normal use of consumer products will often lead to marring, scratching and/or chipping of the surface due to contact with hard objects, contact with brushes and/or abrasive cleansers during normal cleaning processes, and the like.
Thus, there is a need in the coatings art for topcoats having good scratch and mar resistance.